Antioxidant potentials of the pod extract of Caesalpinia pulcherrima Swartz (Fabeace) and the theoretical evaluation of the antioxidant property of the isolated compounds

Abstract

Various diseases associated with oxidative stress have necessitated the need to investigate plants for antioxidant agents. This study aims to investigate the antioxidant potential of the extract and fractions of C. pulcherrima and estimate the quantum chemical properties of polyphenolic compounds isolated from its most active antioxidant fraction. Methanolic extract and partition fractions of the pods of the plant were assayed for their antioxidant activity using four models: 1,1-diphenyl-2-dipicrylhydrazyl radical scavenging, ferric reducing antioxidant power, total antioxidant capacity and hydroxyl radical scavenging activity. Total phenolic and flavonoid contents of the extract and fractions were also investigated. Furthermore, the quantum chemical properties of two polyphenolic compounds were calculated to predict the antioxidant potential. The extract exhibited good antioxidant activity with IC50 = 45.63 µg/ml comparable to ascorbic acid of IC50 = 37.94 µg/ml, high reducing power with value at 376.74 ± 6.78, total antioxidant capacity obtained at ascorbic acid equivalence of 383 ± 8.16 mgAAE/g and potent hydroxyl radical scavenging activity with value at 580.97 µg/ml with ascorbic acid at 30.7 µg/ml. The total phenol and flavonoid contents values at 540.53 ± 3.71 and 347.87 ± 7.13 respectively. Furthermore, the results obtained from the quantum chemical calculations reveals polyphenolic compounds; 5(4-hydroxyphenyl)-3-hydroxy-2-methoxyphenol and 3(4-methanetriiol-2,6-dihydroxyphenoxy)-3’, 4’, 5’, 5, 7-pentahydroxy flavonol as promising antioxidant agents. The study concluded that C. pulcherrima pods have good antioxidant activity. Also, the polyphenolic compounds are among the chemical constituents responsible for the antioxidant activity obtained for the extract and ethyl acetate fraction.